Genes coding for small peptides have been frequently misannotated as long noncoding RNA (lncRNA) genes. Here we have demonstrated that one such transcript is translated into a 56-amino-acid-long peptide conserved in chordates, corroborating the work published while this manuscript was under review. The Mtln peptide could be detected in mitochondria of mouse cell lines and tissues. In line with its mitochondrial localization, lack of the Mtln decreases the activity of mitochondrial respiratory chain complex I. Unlike the integral components and assembly factors of NADH:ubiquinone oxidoreductase, Mtln does not alter its enzymatic activity directly. Interaction of Mtln with NADH-dependent cytochrome b5 reductase stimulates complex I functioning most likely by providing a favorable lipid composition of the membrane. Study of Mtln illuminates the importance of small peptides, whose genes might frequently be misannotated as lncRNAs, for the control of vitally important cellular processes.

Investigation of archeological and paleontological artifacts at the molecular level has become a trend over the recent years. Paleogenomics provides information about the evolution of ancient species; paleoproteomics was recently established as branch of conventional proteomics dedicated to the study of proteomes of extinct organisms. At the same time paleolipidomics, which could focus on the investigation of lipids of ancient species, is not developed yet, though the investigation of fossil lipids may have potential to provide information about past diseases or diet. Here we present the investigation of an ancient fossil bone of a Siberian mammoth using combined proteomics and lipidomics approaches based on high-resolution tandem mass spectrometry coupled with liquid chromatography (LC-MS/MS). Using various experimental approaches, we have reliably identified 98 proteins and 73 lipids in three tissue regions of the mammoth bone. We have also compared the proteome profile of ancient mammoth bone with those of a modern elephant.

Background: Lipids contained in milk are an essential source of energy and structural materials for a growing neonate. Furthermore, lipids' long-chain unsaturated fatty acid residues can directly participate in neonatal tissue formation. Here, we used untargeted mass spectrometric measurements to assess milk lipid composition in seven mammalian species: humans, two macaque species, cows, goats, yaks, and pigs. Results: Analysis of the main milk lipid class, triacylglycerides (TAGs), revealed species-specific quantitative differences in the composition of fatty acid residues for each of seven species. Overall, differences in milk lipid composition reflect evolutionary distances among species, with each species group demonstrating specific lipidome features. Among them, human milk contained more medium and long-chain unsaturated fatty acids compared to other species, while pig milk was the most distinct, featuring the highest proportion of long-chain polyunsaturated fatty acids. Conclusions: We show that milk lipidome composition is dynamic across mammalian species, changed extensively in pigs, and contains features particular to humans.

Background Lipids contained in milk are an essential source of energy and structural materials for a growing infant. Furthermore, lipids' long-chain unsaturated fatty acid residues can directly participate in infant tissue formation. Here, we used untargeted mass spectrometric measurements to assess milk lipid composition in seven mammalian species: humans, two macaque species, cows, goats, yaks, and pigs.Results Analysis of the main milk lipid class, triacylglycerides, revealed species-specific quantitative differences in the composition of fatty acid residues for each of seven species. Overall, differences in milk lipid composition reflect evolutionary distances among species, with each species group demonstrating specific lipidome features. Among them, human milk contained more medium and long-chain unsaturated fatty acids compared to other species, while pig milk was the most distinct, featuring the highest proportion of long-chain polyunsaturated fatty acids. ConclusionsWe show that milk lipidome composition is dynamic across mammalian species, changed extensively in pigs, and contains features particular to humans.

No abstract